Continuous production of polymerization products of acetylene



Jan. '24,' 1939. R. sTADLER Er AL 2,145,058.

kCONTIINLIOUS PRODUCTION OF POLYMERIZATION PRODUCTS OF ACETYLENE Filed June 19, 1957 'Robert smouer' Ka'r Haber?,

INVENTORS TH ETR ATTORNEYS Patented Jan. 1939 CONTINUOUS 2,145,051: o monncrroN oF rounraa1- za'rloN raonUc'rs on ACETYLENE- l :Robert siedler, Heidelberg, and. mi neben,

' Ludwigshafen-on-the-Bhine, Ge

muy, $851811' ors to I. G. Farbenindnstrie Aktiengesellschaft,A

Frankfort-.on-the-Main, G

1937, serial No. 149,138

Application June 19,

In Germany The present invention relates to an improved process for the continuous production of polymerization products of acetylene.

In a copending application Ser. No. 33,072 led July 25, 1935 one of the present inventors andanother have described oan improved process for thekcontinuous preparation of polymerization products of acetylene by meansl of a catalytically acting acid cuprous salt solution in which process acetylene or a ga's containing acetylene (such as the gases obtainable by the thermal decomposition of hydrocarbons, such as methane, for example by treating them in the electric are) is led intol the said cuprous salt at such a 10W temperature that the'gas escaping from the said solution is practically free from polymerization products of acetylene and when working with gases poor in acetylene free from acetylene itself,

while the cuprous salt solution is continuously withdrawn from the absorption plant and introduced into a regenerating plant, the reaction peermany.

June 23, 1936 v 4 Claims. (Cl. 260-678) riod being so limited that the principal polymerization product ismono-vinylacetylene. From the gas mixture escaping from the regenerating plant the polymerization products obtainedl are separated while the residual gas containing acetylene in a concentrated. fonn may be added to the` The regenerated cuprous salt,

a low temperature that the gases escaping from the solution are practically free from polymerization products of acetylene, the solution being then returned to the regenerating plant. The catalytically acting acid cuprous salt solution employed in the said process may contain' an ammonium salt or a salt of a tertiary amine l but there may be employed instead of nitrogen bases and their lsalts also the salts of an alkali f being especially suitable. -From thev cuprous saltsv cuprous chloride is preferably employed.. The temperature of the acid cuprous salt solution in the absorption plant depends on the speed o f the,-

acetylene or acetylene gas employed. Generally speaking temperatures up toa out 40 C. are suitable.

When working up in the manner described in lthe said application Ser.' No. 33,072 gases poor in acetylene, such as the gases resulting from the thermal treatment of hydrocarbons of the kind oi methane, as for example by treating them in the electric are, which gases contain up to about 'through/the catalytically acting acid cuprous salt solution after this solution has been treated with the gas poor in acetylene. In this Way it is possible to increase the yield of acetylene polymers so that the utilization of the heat duringv the regeneration of the absorption solution on the one,` hand and of the cooling during the subsequent separationoi the polymerization products on the other hand is improved.

Theconcentrated acetylene may be supplied to the said cuprous saltsolution already laden with the acetylene from `the gas poor in acetylene either in a further special absorption column or before the entry of the absorption solution into the regeneration plant or at both places. The

concentrated acetylene used may be the pure gas, as for example acetyleneobtained from carbides, but lt isespecially advantageous to use the residual gas rich in acetylene escaping during' the regeneration of the cuprous salt solution in the process according'to the said copending application Ser. No. 33,072.

As already stated above this residual gesenriched in acetylene may-#in the process according to the saidl copending application-be returned into circulation by mixingit with fresh gas. By returning, however, in this way the whole of the enriched acetylene to afresh gas poor in acetylene the concentration of the acety-v 4lene in the fresh gas ymay beincreased to such an extentthat when the gas is led-through'the acid cuprous salt solution at such. a low tempera'- ture that l.therg'as escaping from this solution is practically free trompolymerization products of acetylene, the acetylene is no longer completely vzo absorbed by the solution and thus partly lost with the waste gas.

It according to the present invention, however, the residual gas enriched in acetylene and remaining in the regenerationof the cuprous salt Y solution after the separation of lthe polymerization'products be not returned to the fresh sas but the absorption vessel employed in this stage of the process in the same direction as the cuprous salt solution, It is thus possible to circulate the absorption solution with the aid of the gas current itself according to the principle of the mammoth pump (see Hiitte, Des Ingenieurs Taschenbuc 25th edition, 1926, Volume II, page 864) while dispensing with special circulatory pumps. Since such pumps are attacked by the acid cuprous salt solutions, the said principle is especially advantageous in this case. -Depending on the acetylene content which the residual gas rich in` acetylene still has after passage through the absorption solution, it may now be wholly or partly mixed with the fresh gas or returned' to the enriched acetylene escaping from the regeneration plant. A l

The process according to our present invention will be further described with reference to the accompanying drawing for the working up of a l residual gasrich in acetylene obtained by the regeneration of a cuprous salt solution laden with acetylene, but the invention is not restricted to the particular arrangement showndiagrammatically in the drawing. l

Referring to the drawing, a gas obtained from methane in the electric arc and containing about 18 per cent of ,acetylene is conveyed from a gas holder I by means of a pump 2 into the bottom of an absorption column I kept at low temperature, -through which there is led in the same direction as the gas an acid cuprous chloride solution containing an ammonium salt or an alkali metal salt'or a salt of the alkaline earths, the temperature in the column being kept so lowthat a gas practically free from acetylene and polymerization products of acetylene leaves the column 3. The absorption' solution thus laden with acetylene but, corresponding to the low partial pressure of the acetylene in the gas to be .worked up, by no means saturated therewith, is

supplied without increase in temperatiu'e to the bottom of a second absorption column 4 into and through which there is led in the same direction by means of a pump il the residual gas enriched in acetylene from the gas holder Il. A further amount of acetylene is thus absorbed by the cuprous chloride solution in the column 4. The

' gas now of the lower acetylenev content leaving the column 4 is free from polymerization products of acetylene by reason of the low temperature of the column 4. It may be led in part to the gas holder i and in part be returned to circulation through the gas holder Ill.

'I'he acid cuprous salt solution flowing vout from the column 4 is now heated to such a temperature in the column that the polymerization products of acetylene together with the unchanged acetylene escape. The water vapour which escapes at the time is condensed in the condenser 1 and returned to the column I; the

l :risuonaY means of thepu'mp gas is fmther dried drying tower @,whereuponthe polymerization products are condensed and separated by cooling in the separator l. The

`non-polymerized acetylene-passes as a concentrated gas to the gas holder-ld,` The regenerated cuprous salt solution: is- 'continuously conveyed intovthe column 3 v ectedin the gas -the column 5. by

degasiiication of fsaltsolution on the simultaneously part in this enriched gas of the acetylene on the othervghfandrand., n part, as above described, toth absorption geumn 4 in which ofthe tylene contained by reason of its high acetylene pressure..

Numerou"'modiilcations' of -the described methodof working are possible. For example the acetylene may be led in counter-current in the column 3 instead of in the same direction as ,how our present invention can be carried out in Vpractice but the invention is not restricted to..this example.

- v A Example A \Iri this example a concentrated residual gasis ledfrom the gas holder I0 only. into the column 4, but not also into the regeneration column 5.

25,0 litres of a fresh gas obtained by treating methane in the electric arc and containing be# sides hydrogen 18 percent of acetylene and simultaneously 9 litres of waste gas from the column 4 ,containing about 30 per cent of acetylene are supplied per hour to the gas holder I. The con tent of acetylene in the mixed gas thus obtained is therefore about 18.5 per cent. This gas is treated at C. with an acid cuprous chloride solution containing about 2l per cent by weight of common salt in the column 3, the gasand solution flowing in the same direction from the bottom to the top of the column. The waste gas escaping from the column 3 contains only about 1 per cent of acetylene. The absorption solution passes from the-top of the column 3 to the bottom of the column 4 'and is treated therein at 30 C. with the gas containing about 40 per cent of acetylene taken from the gas holder I0 while flowing in the same direction as the gas. Apart from the 9 litres of wastegaswhich as vstated above are mixed per hour with the fresh gas, the gas leaving the column 4 and containing about 30 per cent of acetylene is led back into the gas holder In. The cuprous chloride solution with- -drawn from the column 4 is introduced into the columnl ifand heated therein to 85 C., a gas being set free which contains, -in addition to water vapour, 14 per cent of vinylacetylene and polymerization products of acetylene of higher boil' 5 through the pipes I3 and I4.

cent oi other gases. The water vapour is con- 'densed by external cooling with water in the conescaping from the separator contains 85 per cent of acetylene and is also supplied to the gas holder IU.

a pump I2.

The condensate recovered in the separator 9 consists to the extent of 85 per cent of monovinylacetylene. Thus, of the acetylene introduced per hour 94 per cent is obtained in the form ofpolymerization products of acetylene and per cent in theform of pure monovinylacetylene. t

Instead of introducing the residual gas from the gas holder III only into the column 4 as described in detail in the preceding example it may be introduced into both the columns 4 and Furthermore, the cuprous chloride solution may be led from column 3 directly to the regenerating column 5 through the pipe I5 indicated by in the annexed drawing and treated therein with an appropriate amountof the residual gas from the gas holder I0. Instead of the said residual gas other gases rich in acetylene or .pure concentrated acetylene may be employed.

'What we claim is:

1. A process for the continuous preparation of I'he regenerated cuprous chloride solutionv is cooled down to 30 C. in the cooler 5 and cir-- culated to the absorption column 3 by means of polymerization productspof acetylene'by means of a 'catalytically acting acid cuprous salt solution from gases poorl in acetylene which comprises continuously leading in a irst absorption vessel a gas poor in acetylene through the catalytically a'cting solution at such a low temperature that the gas escaping from said solution is practically free from polymerization products of acetylene and from acetylene itself, continuously withdrawing from the rst absorption vessel the cuprous salt solution containing therein the absorbed acetylene, introducing it into a second absorption vessel and continuously leading therein through the said solution a gas rich in acetylene. and continuously discharging from this solution the reaction products and absorbed acetylene at such a temperature that -the main reaction product is monovinyl acetylene, and continuously returning the regenerated catalyst solution to the first absorption vessel.

2- In the process according to claim l the step which comprises discharging the reaction products and the absorbed acetylene from the vessel into which the gas' rich in acetylene is intro duced.

3. In the process according to claim 1f the step which comprises discharging the reaction products and the absorbed acetylene after withdrawing the cuprous salt solution from the second absorption vessel in a special discharging vessel.

4. In the process according to claim 1 the step which comprises using as the .gas rich in acetylene the acetylene discharged from thecuprous salt solution used as an absorbing liquid. 

